posts tagged with the keyword ‘rhino’

2015.05.03

You can’t have a turntable without an arm! Well, I guess you could, but where would you put the pen? Here’s some of the design files for the arm. The hole pattern on the larger part was made to match a servo hub from SparkFun, which is also from ServoCity, which provided a STEP file. (Ignore the heart-shaped thing for now. It’s experimental!)

Luckily I was able to open the STEP file in both Rhino and in FreeCAD! It’s like I won the CAD file lottery or something. But seriously, if there’s ever a competition to convert from one format to another and then another and another… I think I can win.

I was able to get what I needed to get the hole spacing right, which is all I really needed this time. The holes are tapped for 6-32 screws. Once again I’m mixing Imperial and Metric. Sigh… Mission (somewhat) accomplished, I guess.

The arm consists of three layers of laser-cut pieces stacked up, and screws to hold them together. I played around with materials a little bit, trying wood in the center, but finally choosing the red acrylic. I thought about clear, but there is at least one other red element right now, and possibly more to come, so I chose the black and red combo. Always a good choice!

There’s also a hinge I cut from a 1mm thick plastic I got from the Midland scrapyard. (Windell from EMSL thinks it might be polypropylene.) The laser cut it fine once I figured out the proper settings… and covered it with masking tape on both sides.

And yes, I did borrow a few ideas from the Egg-Bot design. Sharpies, FTW! Pen holder designers unite, and all that. There’s a 8-32 square nut in there, really snug. I do not have a nice thumbscrew like EMSL uses… yet!

If I were to provide assembly instructions I’d probably want such a drawing. Here are some notes on the process, so I can do it again next time.

In Inkscape, each piece must be an object. The ‘holes’ cannot be separate objects, but must be cut out (differenced) from the main object. (This is the same method needed when bringing a 2D drawing into OpenSCAD, so nothing new there.)

Sadly, Rhino cannot import SVG files. (Mini-rant: I’m always surprised at the number of applications that do not support SVG. The SVG specification has been an open standard from the WC3 since 1999!) Rhino can import PDF files, so export your Inkscape file as a PDF. Your PDF should be a vector PDF, by default. Inkscape should do the right thing unless you’ve done something silly to your file. (Which is possible, I’ve done it.)

Our vector file is now in Rhino! Double-check to make sure each line/object did not get doubled-up. I’ve had it happen a few times but could not conclusively determine what causes it. It may be the width of the stoke of the objects in Inkscape.

You can now extrude your object(s) in Rhino. I make them the height of the material I am using. Oh, I’ll be laser cutting these pieces with 4.45mm acrylic. YMMV.

Change the view in Rhino from wireframe to solid and you’ll see your new 3D object(s)…

Make sure the holes are really holes! If not, re-read the part above about objects and holes and such. You need to difference any cut out things!

Now you can move your new object(s) because the original vector lines we imported in are probably sitting right underneath them. Swing your object(s) into the view you want… get that angle just right, and then choose “Make 2-D Drawing” from the “Dimension” menu.

You should now have a 2D version of your 3D object. Rhino should also select it by default, so you can use the “Export Selection” menu to save it out as… A DXF file. :( Sadly, Rhino cannot export as an SVG or vector PDF, or even an EPS file. Rhino can export as an Illustrator file (.ai) but Inkscape cannot open those. The AI file it exports starts with “%!PS-Adobe-3.0″ which is probably a format from that was popular in the 1990s.

Anyway, we can certainly import that DXF file back into Inkscape and work with it, and make it look like a nice vector drawing. Mostly. Sort of. I mean, if you want to just fill it with a color or change the stroke, it’s not quite that easy. If you just want a line drawing that isn’t too fancy, mission accomplished!

Oh, and not that I want to turn Inkscape in a 3D application, but I could see great value in being able to extrude and change the view angle of a vector drawing… maybe through an extension?

2015.02.24

A big part of the work I do is the process, and trying to find tools that fit the way I work, and are also available. “Available” may mean open source, or free (as it beer) or multi-platform, or some other criteria I come up with.

In my Digital Craft class we’ve used RhinoCAM to generate the G-code needed to run the 4×8 CNC router in the DCRL. RhinoCAM has a lot of options, as it should for a full-on commercial package. Meanwhile, I’ve been working on a Shapeoko2, which is a small and affordable hobby-level CNC machine. For a machine like this, I’d like to use a workflow that doesn’t require expensive commercial software, because at some point I may not have access to Rhino and I’ll need tools I can afford.

(I should note that I have used CamBam in the past, but being commercial software that is Windows-only doesn’t entice me to want to use it again.)

I’ve played a little bit with Easel from our friends at Inventables, but I’m also not a fan of hosted solutions that can disappear, or start charging for access, etc. At this point I start to sound extremely picky, but really, I’m just looking for tools I can rely on, that are not expensive, and run on the platforms I use. (Easel is actually really nice, and while it’s easy to use, I think that comes at the price of hiding some of the complexity and advanced features I want to learn. Still, if you just want to cut/carve/engrave, check it out.)

I stumbled up MakerCAM, and there’s a bunch more info about it on the Shapeoko wiki. Basically it’s a Flash application (!) that you can use online, or download and run offline, which provides all the basic needs of a CAM application. And it actually works.

I started as I often do, drawing a 2D vector file in Inkscape. (Oh, I should mention there is an extension for Inkscape called Gcodetools, but we’ll skip that for now.) Once I had my Inkscape file I saved it as an SVG, as you normally would with Inkscape.

I then loaded the SVG into MakerCAM. Note that if you load an SVG from Inkscape you need to set the px/inch to 90 in the preferences. Once in MakerCAM it’s fairly easy to create the toolpaths and generate the G-code. If in doubt, check out the help page and the tutorial page for all the info.

After exporting my G-code file I was able to load it into the Grbl Controller and run it on the Shapeoko. Now, Grbl Controller is no Mach3, but it’s also open source, and multi-platform, so there’s that. (Yes, I know the image above does not match the first two images, that’s because I went crazy with the hatch fill from the Egg-Bot extension for Inkscape. Just pretend you know what I’m talking about.)

Oh, if you want to “run” your G-code before you run your G-code to make sure it’s doing what you think it’s doing, check out OpenSCAM, which is a nice little simulator.

(And yes, I know of Chilipeppr for Grbl, but I’ve not dug into it yet.)